Fluidic system trimmable elements



I United States Patent [1113,545,467

[72] Inventors Clyde C. K. Kwok; 56 References Cited Sharp Quebec UNITED STATES PATENTS Canada 1,928,295 9/1933 Lusher 251/90x [21] Appl. No. 751,091

2,271,146 1/1942 NOll'lS 251/90X [22] Filed Aug. 8, 1968 3,280,037 10/1966 Gordon et al.... 251/93 [45] Patented Dec. 8, 1970 3,380,655 4/1968 Swartz 137/81.5X [73] Assignee Aviation Electric Limited 3,410,289 11/1968 Dexter 137/815 St. Laurent, Montreal, Canada [32] Priority Aug 9, 1967 3,420,255 1/1969 Wilkerson 137/815 [33] Canada 3,442,279 5/1969 Swartz 137/815 [31 No. 997415 Primary Examiner-Samuel Scott Attorney-Stevens, Davis, Miller & Mosher [541 1C 'IglMMABLE ELEMENTS ABSTRACT: A fluidic system control element having a body alms rawmg with a first duct for the discharge of a power jet and a second [52] [1.8. CI. 137/815 duct for the reception of part of the power jet stream. A third [51} lnt.Cl. Fl5c l/04 duct and a compensating jet means direct a control stream [50] Field of Search. 137/815; which can be adjusted initially and set to compensate for dif- 251/90, 93. 1 15 ferences in manufacturing tolerances.

PATENTEU DEC 8 mm 13545467 sum 3 or 3 FIG] FLUIDIC SYSTEM TRIMMABLE ELEMENTS This invention relates to elements for fluidic systems, that is to say systems in which a low-pressure fluid-power source is used to control or modulate a higher pressure, and systems in which a small fluid flow is used to control a larger fluid flow.

Many devices have been developed in recent yearsin which a fluid stream is controlled by means of a much smaller fluid stream. Typical devices of this type include a fluid power jet discharging through a nozzle into two outlet passages spaced downstream of the nozzle exit. One or more control jets, impinging (usually normally) on the power jet provide a means for influencing the direction of the power jet and thus for determining the portion of the power jet entering each outlet passage.

These fluidic system elements or devices, known generally as fluidic amplifiers, perform functions which are analogous to those now being performed by electronic components. Nu merous techniques have been developed to fabricate such devices, (e.g. epoxy castings, etching into photosensitive materials and injection molding). However, one of the major problems encountered in the manufacture of fluidic amplifiers is the inconsistency between elements which are fabricated from the same tooling. Such inconsistencies result from both geometric and surface variations associated with fabrication techniques and amplifier inlet velocity profile distortions associated with interconnection channel effects.

Among all the fabrication techniques used to date, injection molding is considered to be capable of produlping the most consistent results. However, there is still an appreciable variation in performance of amplifiers manufactured from the same batch using this technique. It has been found that the desired degree of consistency for some critical circuit applications cannot be achieved with the present state of the art in injection molding techniques. Alternative fabrication methods do not offer superior consistency and do not have the economic advantage in large volume production.

An object of the present invention is the provision of an improved fluidic system element which can be manufactured by existing techniques to have predetermined and reproducible operating characteristics.

According to one aspect of the present invention, a fluidic system element includes a body formed internally with a first duct for the discharge of a power jet of operating fluid flowing from a supply duct, with a second duct for the reception of at least part of 'that power jet, and with a third duct for the discharge of a control stream of operating fluid capable of causing variation of the fraction of the power jet received by the second duct, together with compensating stream delivery means arranged to discharge an adjustable but predetermined amount of operating fluid also derived from the supply duct to join and to influence the direction of flow of the power jet, whereby the element can be initially set or calibrated by means of adjustment of the compensating stream delivery means.

According to another aspect of the present invention, a fluidic system element includes a body formed internally with a first duct for the discharge of a power jet of operating fluid flowing from a supply duct, with a second duct for the reception of at least part of that power jet, and with a third duct for the discharge of a control jet of operating fluid capable of causing variation of the fraction of the power jet received by the second duct, together with compensating jet means arranged to direct an adjustable but predetermined amount of operating fluid also derived from the supply duct to intersect and thus deflect the power jet, whereby the element can be initially set or calibrated by means of the compensating jet means.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of a fluidic system element according to the present invention;

FIG. 2 is a sectional plan view of the element shown in FIG. 1, and is taken on the line II-II of FIG. 3;

FIG. 3 is a sectional front elevation taken on the line III-III of FIG. 2;

FIG. 4 is a fragmentary front elevation of part only of the element as shown FIG. 3, and is drawn to a larger scale than that FIG:

FIG. 5 is a diagrammatic representation in the form of a sectional plan view showing faulty. operation of an element similar to that shown in FIG. 2 but to which the present invention has not been applied;

FIG. 6 is a diagrammatic representation in the form of a sectional plan view showing the improved operation of the element shown in FIG. 2; and j FIG. 7 is a sectional plan view similar to FIG. 6 but showing the velocity profiles at spaced locations in the fluid flows.

Referring first to FIG. 1, the fluidic systems element shown therein is a stream-interaction device having a body 1 formed by an upper part 3 and a lower part 5 held together by four tubular rivets 7, this body having dimensions of approximately 2cm. by 3cm. by 0.7 cm. Clamped between the two parts of the body are a supply tube 9, two control tubes 11 and 13, and two output tubes 15 and 17. The lower body part 5 is formed on its upper surface with grooves which, when the upper body part 3 is clamped in place, are closed by the upper part to form ducts or channels which intersect to permit the interaction of fluid streams flowing therethrough.

These ducts or channels are shown in FIGS. 2 and 3, and comprise a power jet nozzle 19 connected by a duct 29 to the supply tube 9; a first control jet nozzle 21 connected by a duct 31 to the control tube 11; a second control jet nozzle 23 connected by a duct 33 to the control tube 13; a first output port 25 communicating with the outlet tube 15 and a second output port 27 communicating with the outlet tube 17. The power jet nozzle 19 is directed towards the sharp corner of a splitter 41 which separates the two outlets ports 25 and 27. An exhaust port 43 disposed between outlet port 25 and the control jet nozzle 21, and an exhaust port 45 disposed between outlet port 27 and the control jet nozzle 23., both extend outwardly and terminate in ports in the side walls of the element.

The lower body part 5 is also formed with a further compensating jet nozzle 51 extending from the duct 29 to a point adjacent the discharge end of power jet nozzle 19, and directed towards the discharge from nozzle 19 at an inclination from the same side as is the control jet nozzle 21. A similar compensating jet nozzle 53 is provided on the opposite side of the power jet nozzle 19, and is directed towards the discharge from nozzle 19 at an inclination from the same side as is the control jet nozzle 23. Each jet nozzle 51 and 53 is provided intermediate its ends with an enlargement formed by a transversely extending cylindrical bore 61 or 63 which extends to the upper face of the upper part 3, as shown most clearly in FIG. 4. The parts of these bores in the upper part 3 are screwthreaded and fitted in these bores are respectively two grub or set screws 71 and 73.

The fluidic systems element which has been described is conventional in its operation apart from the provision and action of the compensating jet nozzles 51 and 53 with their grub screws 71 and 73. As shown in FIG. 5 for a device from which these parts are omitted, fluid supplied under pressure through the supply tube 9 to the power jet nozzle 19 is discharged across the open space where the various nozzles and ports meet, directed towards the sharp corner of the splitter 41. Ideally, in the absence of any disturbing jet discharged from the control jet nozzles 21 and 23, this power jet from nozzle 19 is divided by the sharp corner of splitter 41 into two equal streams which pass respectively into the two outlet ports 25 and 27. In practice, it is difficult to ensure that the two streams are equal, since minor surface differences between two consecutively produced devices using the same manufacturing machines usually have dissimilar characteristics. Thus usually the element as manufactured will produce an unequal distribution of the power jet stream from nozzle 19, as indicated in FIG. 5.

In use of the element, a control stream discharge from one of the control jet nozzles 21 and 23 is used to deflect the main power jet to change its distribution between the two outlet ports 25 and 27. Again, since the initial undisturbed distribution of the power jet can be ascertained only by measurement or calibration, it is not possible to predict accurately the performance of a standard production element.

The operation of the improved element of the present invention will be understood from a study of FIGS. 5, 6 and 7. When the element of FIG. is modified by the inclusion of the two compensating jets 51 and 53 with their grub screws 71 and 73, and an additional flow of the fluid from the duct 29 can be provided if desired. Thus with both of the grub screws 71 and 73 screwed fully home to block their associated compensating jets 51 and 53, no discharge of fluid takes place through either compensating jet and the mode op of operation is identical with that shown in FIG. 5. By retraction of the grub screw 73, a suitable'discharge of fluid through the compensating jet 53 can be selected which will divert the power jet from nozzle 19 so that it is equally divided between the two outlet ports 25 and 27. As will be clear from FIGS. 1 and 3, the two grub screws 71 and 73 are accessible through the small bores 61 and 63 from the top of the. element, and if desired once the manufactured element has been correctly set or calibrated during the inspection stage of its manufacture, the upper ends of these holes can be filled with a suitable initially plastic but hardening material to ensure that the grub screws do not become dislodged either by vibration or by tampering.

It will be clear that if desired one of the two compensating jet nozzles can be eliminated if the element is designed always to produce a power jet which is displaced to one side of the desired central position. When this is done, the single grub screw will be adjusted to produce a discharge from the single controlled compensating jet such as to produce the desired accurately central power jet.

FIG. 7 illustrates the operation of the element in more detail. Normally,-if the geometric configuration of the design is perfectly symmetrical and the surface finish is absolutely even, the power jet from nozzle 19 should be split equally between the two outlet ports 25 and 27. In the case where inconsistency has developed, (e.g. the power jet leans toward the right), erroneous output conditions will result. By opening the right control by an appropriate amount, the impinging of the compensating jet on the power jet will cause the latter to deflect to the opposite direction. The amount of deflection is directly proportional to the magnitude of the compensating jet momentum vector component which is normal to the power jet. The momentum vector component of the compensating jet which is in the same direction as the power jet causes distortion of the velocity profile taken across the jet stream, e.g. as shown in FIG. 7, and eventually turns the jet towards the opposite wall. These two effects are additive. Similarly, if the jet originally is biased toward the left, the left compensating jet is then used to provide the corresponding correction.

Both compensating controls may be opened simultaneously to provide controllable variation of the power jet velocity profile and thereby achieve improved gain of the fluidic amplifier.

The invention is not limited in its application to fluidic system amplifiers of the type described and illustrated above. Thus it can be applied to a wall attachment fluidic device to provide means for obtaining identically equal absolute switching pressures in bistable amplifiers and for achieving maximum gain in monostable amplifiers. In jet-on-jet proportional devices, the invention provides means for obtaining equal splitting of the power jet in the absence of a control signal.

It will be seen that by the present invention is provided what may be called a trimmable fluidic amplifier, the word amplifier" being used in the widest possible sense to include devices such as flip-flop devices and fluidic oscillators.

In the case of fluidic oscillators, the invention enables the operation to be modified in a manner equivalent to modification of the internal geometry of the device, so that it is possible in suitable cases to vary the frequency of operation of the fluidic oscillator.

The fluidic system elements which have been described above can provide the following advantages:

l. The trimmable fluidic amplifier is normally adjusted for one specific power jet pressure. As the power jet pressure is increased, a corresponding increase in compensating jet magnitude will be required. Since the compensating jets are designed to have the same source as that of the power jet, the required increase is automatically provided;

2. Once the control is adjusted, the setting should provide correct functioning indefinitely. In other words, the reliability of the fluidic device will not suffer by the inclusion of this trimming feature;

3. Due to various limitations encountered in the manufacture of fluidic devices, it is extremely difficult to fabricate bistable amplifiers with identical control switching pressures. There are many possible reasons; the power jet can be slightly biased, or the two control input impedances may be different. This trimmable control can provide the proper correction by appropriately deflecting a corresponding amount of the power jet to compensate for the error;

4. The basic design principle of the fluidic wall attachment monostable amplifier utilizes the unbalanced venting technique which involves additional venting to ambient of the normally inactive wall attachment bubble region. This imposes a more stringent requirement on the perforrnance repeatability of the monostable amplifier than on that of the bistable amplifier. Variation in bias vent" affects the amplifier stability level as well as gain characteristic. The incorporation of this adjustable control in all fluidic monostable amplifier designs will not only provide easy optimization of amplifier performance but also the means to produce consistent monostable elements; and

. In the production of jet-on-jet proportional fluidic amplifiers, the major difficulty involves the process of achieving equal splitting of the power jet. Moreover, if the fluidic operational amplifier is subjected to unbalanced output loading conditions, it is generally desirable to devise means to compensate for such effects.

The trimmable control jet configuration can not only provide a solution to the aforementioned problems, but can also create a controlled distortion of the power jet velocity profile, and subsequently, the gain of the device.

We claim:

1. A fluidic system control element including:

a. a body;

b. a supply duct in that body;

c. a first duct in that body in communication with the said supply duct and arranged for the discharge of a power jet of operating fluid flowing through the said first duct from the said supply duct;

d. a chamber in the body arranged to receive the power jet discharge from the said first duct;

e. a second duct communicating with the said chamber and arranged to receive a variable part of the said power jet discharge from the first duct;

f. a third duct arranged to discharge into the said chamber a control stream of operating fluid;

g. supply means arranged to supply the third duct with fluid to constitute the said control stream, and independent of the said supply duct;

h. a fluid flow passage separate from said third duct and extending between the said supply duct and the said chamber and communicating with the said chamber in such a manner that it discharges into the chamber a compensating stream also derived from the supply duct and effective to influence the direction of flow of the power jet; and

i. an adjustable restriction in the said fluid flow passage; and whereby the element can be initially set or calibrated after assembly by adjustment of the said adjustable restriction.

2. A fluidic system control element according to claim 1,

and in which:

the said adjustable restriction is an adjustable plug effective to restrict the said fluid flow passage to a variable degree.

LII

3. A fluidic system control element according to claim 1, and in which:

a. the said body is formed with a screw-threaded bore which meets the said fluid flow passage; 7

b. a screwed plug is mounted in and is complementary to the said screw-threaded bore;

c. the said plug is accessible from outside that body for rotation and thus for a change in its restrictive effect on fluid flow through the said fluid flow passage, at least until the control element is assembled during manufacture to a point where the operating characteristics of the device can be ascertained; and

d. said plug constitutes the said adjustable restriction.

4. A fluidic system control element according to claim 1,

and in which: y

a. the said body is formed with ascrew-threaded bore which meets the said fluid flow passage;

b. a screwed plug is mounted in and is complementary to the said screw-threaded bore;

c. the said plug is accessible from outside the said body for rotation and thus for a change in its restrictive effect on fluid flow through the said fluid flow passage, at least until the control element is assembled during manufacture to a point where the operating characteristics of the device can be ascertained;

d. said plug constitutes the said adjustable restriction;

e. said plug is contained completely in the said screwthreaded bore when in operative position partly to restrict flow through the said fluid flow passage; and

tithe end of the said screw-threaded bore remote from the said fluid flow passage is filled in the completed element with a substance inhibiting further rotation of the said plug. i 5. A fluidic system control element including:

a. a body;

b. a supply duct in that body;

c. a first duct in that body in communication with the said supply duct and arranged for the discharge of a power jet of operating fluid flowingthrough the said first duct from the said supply duct;

. a chamber in the body arranged to receive the power jet discharge from the said first duct;

e. a second duct communicating with the said chamber and arranged to receive a variable part of the said power jet discharge from the first duct;

f. a third duct arranged to discharge into the said chamber a control stream of operating fluid;

supply means arranged to supply the third duct with fluid to constitute the said control stream, and independent of the said supply duct;

. a fluid flow passage separate from said third duet extending between the said supply duct and the said chamber;

i. compensating jet means at a discharge end of said fluid flow passage and arranged to direct into said chamber a compensating jet of fluid also derived from the supply duct and arranged to intersect and thus deflect the said power jet; and

j. an adjustable restriction in the said fluid flow passage; whereby the element can be initially set or calibrated after assembly by adjustment of the said adjustable restriction.

6. A fluidic control system element according to claim 5, and in which the said compensating jet means is arranged to direct a stream of operating fluid to intersect the power jet with an acute angle between the direction of flow of the stream and the said power jet. 

